The anchovies should be desalted, cleaned, boned and very finely chopped: do the same for the tuna fish, then mix everything together for a final chopping on a wooden chopping board. Dilute this chopped mixture with half of the chicken stock, sieve it and collect in a pot containing the second half of the stock, and the red and white pepper. Over a very low heat, without completely covering, wait for the sauce to become cooked and condensed. As soon as the pasta has been drained, season with the melted butter and the olive oil, parsley and anchovy and tuna purée which will appear as a fairly dense sauce. Stir over the heat for no more than three minutes and serve hot.